Session: 09-01-01: Offshore Wind Energy - Installation

Paper Number: 107904

107904 - Predicting Weather Down Time for an Offshore Wind Turbine Installation Vessel (Wtiv) With Feeders Using Rapid Spectral Rao-Based Hindcast Vessel Motions in Wave Environment 

The relatively new source of alternative energy, offshore wind energy, has brought many new challenges into the logistics and maritime operations in the north America.  “Jones Act Maritime Law” prohibits foreign flagged vessels from transporting cargo within the U.S. territorial sea.  This restriction means Offshore Wind Turbine Installers can either build new Wind Turbine Installation Vessels (WTIV) in the United States, or transport wind turbine generators (WTG) using coastwise qualified feeder vessels and foreign WTIVs.

The constraints on the motion and acceleration of WTG components may limit operations or require motion compensation systems.  To support system design, a tool is required that allows the user to evaluate the difference is uptime between different vessels, load conditions, motion compensation equipment and lifting appliances.  Traditional weather down time analysis evaluates operations against hind cast environmental data.  The method described here expands the weather downtime simulation to include cargo motions and accelerations and vessel responses.  The results can then be used to evaluate the relative value of each feeder type or motion compensation system to inform installation system design, risk analysis and contracting.  

The model is applied to analyze multiple candidate feeder vessels and various turbine models, transit routes, and installation sites covering 41 years of hourly hindcast data.  To accommodate this scope, a technique is applied to rapidly compute vessel motions using pre-computed Spectral Response Amplitude Operations (SRAOs) at each hindcast time step.  The SRAO database has parameters of wave heading (), modal period (Tp), significant wave height (Hs), directional cosn spreading, and spectral shape ().  SRAOs are referenced for each wave condition to approximate motions in wind waves and swell.  This method offers quick turnaround, simulating millions of hours of hindcast vessel motions in a few hours of computational time on a 120-core cluster. Weather uptime for this sensitive operation is drastically increased in some instances when the feeder vessel can be aligned to the predominant wave direction.  By capturing the underlying hydrodynamics in the proposed simulation, the method presented here can be applied to understand project schedule risk and fleet logistics during the project planning stages.  This model can be further leveraged to offer operational guidance to the vessel operator during the wind farm construction phase.

Presenting Author: Melissa Hertel Crowley Engineering Services

Presenting Author Biography: Melissa Hertel is a Senior Naval Architect at Crowley Engineering Services. Melissa specializes in project management and engineering innovation and is currently developing simulation tools and techniques to model marine transportation systems to install offshore wind farms.
This work builds on Melissa’s previous experience as a Project Manager and Lead Project Engineer for Mobil Shipping and Transportation (MOSAT) developing software and performing simulation studies of transportation systems (production facility and storage, loading harbor, fleet of ships, receiving harbor, storage and user) with random events (high wind/waves, low visibility, proximity of marine cyclones or icebergs, plant breakdowns) and other restrictions (vessel drydockings, daylight maneuvering in ports, production or demand schedules).
Past notable projects include Project Manager, Lead Project Engineer & Owner’s Representative for design construction and testing of Seattle’s 108’x27’ Fireboat LESCHI which included the first civilian Chemical, Biological, Radiological, Nuclear and Explosive (CBRNE) crew protection system on a fireboat and San Francisco’s 88’x25’ CBRNE Class II Super Pumper ST. FRANCIS which can pump water at pressures up to 300 psi. Project Manager, Lead Project Engineer & Owner’s Representative for design construction and testing of King County’s 45’x18’, 30 knot, Foil Assist Catamaran Research Vessel SOUND GUARDIAN and California Department of Water Resource’s 60’x24’, 22 knot, Catamaran Research Vessel SENTINEL.
Melissa received her BS in Naval Architecture and Marine Engineering from Webb Institute in 1986, her Professional Engineer license in 1988, her Master of Theology from Fuller Theological Seminary in 1996 and her Master of Business Administration from Georgetown University in 2000.
Ms. Hertel’s publications include: “Using Simulation Programs to Design and Analyze Marine Transportation Systems” and “Design, Analysis and Optimization of LNG Logistics using Simulation Programs”.
When not tackling new engineering challenges, Melissa enjoys traveling and bicycling with her young adult son and has three stadiums remaining in her quest to visit every major league ballpark.

Authors:

Ali Mohtat Crowley Engineering Services
Melissa Hertel Crowley Engineering Services
Christopher Hooper Crowley Engineering Services
Charles Jors Crowley Engineering Services
Benjamin Souquet Crowley Engineering Services
Coulston Van Gundy Crowley Engineering Services